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Santonian Working Group

Subcommission on Cretaceous Stratigraphy

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The aim of each WG is to nominate an internationally acceptable boundary for the base of the stage, plus any substage boundary where appropriate. Candidate stratotype sections should be proposed.

It is recommended we follow the procedures, which aims first to establish a correlation and then define a boundary, i.e. the recommended boundary must be recognisable over as wide an area as possible and ideally in both Tethyan and Boreal Realms. The stratigraphic level of the recommended boundary should conform as closely as ferasible with current practice and the proposals made at the Subcommission's 1995 Brussels Symposium (Rawson et al., 1996, Bulletin de l'Institut Royal des Sciences Naturelles de Belgique, Sciences de la Terre vol. 66 - supplement) are a necessary starting point. Especially, Lamolda, M.A. & Hancock, J. The Santonian Stage and substages, op.cit., 95-102. [abstract] [full text]

Bases of correlation
The following criteria are considered:
  • biostratigraphy
  • cyclostratigraphy
  • event stratigraphy
  • geochemistry (stable isotopes)
  • magnetostratigraphy
  • sequence stratigraphy
The Stratotype section

Choice of the stratotype section will depend primarily on the chosen boundary and although historical precedence should be considered it should not over-ride the importance of choosing a widely correlatable boundary.

Abstract: The recognition of the Coniacian-Santonian boundary is easy with good correlation of macro- and microfossil evidence. The Santonian Working Group (SWG) recommends the lowest occurrence of Cladoceramus undulatoplicatus (Roemer) as the marker for the Coniacian-Santonian boundary. As yet, the SWG cannot make a formal proposal for a Boundary Stratotype Section, because the biostratigraphy must be better known and integrated first. Three candidates for Boundary Stratotype Section, Olazagutia Quarry (Navarra, Spain), Seaford Head (Sussex, England) and Ten Mile Creek (Dallas, Texas, USA) were selected for further decision. To achieve a useful subdivision of the Santonian into substages a better understanding of taxa ranges and correlation through different biogeographic realms is needed. Formal proposals for subdivision would be premature at present, but a three-fold division is favoured.

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buzon Marcos A. Lamolda